Conditioned environmental chambers are used to protect sensitive equipment including various electronic modules from corrosive materials. A hermetically sealed chamber is typically made from titanium or stainless steel. As the volume of equipment and electronic modules increased over time it was necessary to use larger chambers. In a fixed ground position, the extra weight of the large metal chambers was not a significant concern.
Recent applications of sensitive equipment and electronic modules to marine applications make the use of a titanium or stainless steel chamber less than desirable. Composite materials, such as polyester resins or vinyl resins reinforced with glass elements (fiberglass) or carbon fiber are well suited for this use because of their lightweight, ease of manufacturing and flexibility in configurations. Some of the composites are heavily doped with bromide as a fire retardant. When designed for this use, the composites are designed to have a very low level of porosity, being comprised of layers to build them up to the necessary thickness.
Methods and devices for measuring porosity of materials are well known. Unfortunately, they are essentially designed to measure a flow through a porous material rather than a material designed to have a very low level of porosity. The ASTM Standard Test Method For Dye Penetration Of Solid Fiberglass Reinforced Pultruded Stock, Designation: D 5117-03 published in January 2004 is an example of the types of measurements that are made. In this case a dye penetrant test method is used to evaluate solid fiberglass reinforced pultruded rod stock for longitudinal wicking. The specimen being tested is placed on end into the dye penetrant to a specified depth and wicking due to capillary action of the penetrant is observed. This test does not determine porositity of a material and is not suited for testing of porosity perpendicular to the reinforcing fiber.
U.S. Patent Application Publication No. US 2002/0147551 A1 entitled Pore Structure Analysis Of Individual Layers of Multi-layered Composite Porous Materials discloses a method of determining porosity of a multi layered porous material by measuring the flow through the material under pressure. The method uses an indirect calculation and requires that flow through the material occur and be measurable by displacement.
Conventional quantitative methods (ASTM D 5117-03) requires the use of a fume hood to extract and exhaust potentially irritating vapors during the working process. Other tests involve UV radiation and thus require protective eyewear.
Therefore, there is a need for measuring porosity of a material designed to have a very low level of porosity which does not require measurement of the flow of a gas or liquid through the material under test.
There is further a need for measuring porosity of a material designed to have a very low level of porosity which does not require use of irritating vapors or harmful UV radiation.